U.S. patent application number 13/131933 was filed with the patent office on 2011-11-10 for optical tomographic imaging apparatus and imaging method for an optical tomographic image.
This patent application is currently assigned to CANON KABUSHIKI KAISHA. Invention is credited to Futoshi Hirose.
Application Number | 20110273668 13/131933 |
Document ID | / |
Family ID | 42115949 |
Filed Date | 2011-11-10 |
United States Patent
Application |
20110273668 |
Kind Code |
A1 |
Hirose; Futoshi |
November 10, 2011 |
OPTICAL TOMOGRAPHIC IMAGING APPARATUS AND IMAGING METHOD FOR AN
OPTICAL TOMOGRAPHIC IMAGE
Abstract
Provided is an optical tomographic imaging apparatus capable of,
when imaging a tomographic image of an object, monitoring an
incident state represented by an incident position and an incident
angle of a measuring beam group with respect to the object, causing
the measuring beam group to form an image at a predetermined
position of the object, and obtaining the tomographic image at high
speed. The optical tomographic imaging apparatus is featured in
that one of multiple beams emitted from a light source to be split
and multiple beams emitted from multiple light sources are split
into a measuring beam group and a reference beam group, and the
optical tomographic imaging apparatus includes a monitoring device
for obtaining a monitoring image of the object, thereby capable of
monitoring an incident state represented by an incident position
and an incident angle of the measuring beam group with respect to
the object.
Inventors: |
Hirose; Futoshi;
(Yokohama-shi, JP) |
Assignee: |
CANON KABUSHIKI KAISHA
Tokyo
JP
|
Family ID: |
42115949 |
Appl. No.: |
13/131933 |
Filed: |
December 18, 2009 |
PCT Filed: |
December 18, 2009 |
PCT NO: |
PCT/JP2009/071718 |
371 Date: |
May 31, 2011 |
Current U.S.
Class: |
351/206 ;
351/246 |
Current CPC
Class: |
G01B 9/02091 20130101;
G01B 9/02019 20130101; G01B 9/02044 20130101; A61B 3/102 20130101;
G01B 9/0203 20130101; G01B 9/02027 20130101 |
Class at
Publication: |
351/206 ;
351/246 |
International
Class: |
A61B 3/14 20060101
A61B003/14; A61B 3/00 20060101 A61B003/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 26, 2008 |
JP |
2008-331925 |
Claims
1. An optical tomographic imaging apparatus that obtains at least a
tomographic image of an subject's eye based on a plurality of
combined beams obtained by combining a plurality of return beams
from the subject's eye that is irradiated with a plurality of
measuring beams and a plurality of reference beams each of which
respectively correspond to each of the plurality of measuring
beams, the optical tomographic imaging apparatus comprising: an
irradiating device that irradiates an anterior eye part of the
subject's eye with the plurality of measuring beams; a monitoring
device that obtains a monitoring image of the subject's eye; and an
adjusting device that obtains information of irradiated ranges
where the anterior eye part is irradiated with the plurality of
measuring beams by said irradiating device from the monitoring
image, and that adjusts each of the irradiated ranges to be a
predetermined overlapped state based on the information of the
irradiated ranges.
2-4. (canceled)
5. The optical tomographic imaging apparatus according to claim 1,
wherein said adjusting device is configured in at least one of the
following manners that: an area of the anterior eye part, which is
irradiated with the plurality of measuring beams, is adjusted to a
minimum; the relative positions of the plurality of measuring beams
and the subject's eye are recognized by increasing and decreasing a
number of beams of the plurality of measuring beams; a scanning
range of the plurality of measuring beams is increased and
decreased; a gaze is shifted by using a fixation target at which
the subject's eye is to be guided; and a face fixation unit that
supports a face of an examinee at a predetermined position is
shifted.
6. The optical tomographic imaging apparatus according to claim 1,
wherein said adjusting device adjusts relative positions of the
plurality of measuring beams and the subject's eye.
7. The optical tomographic imaging apparatus according to claim 1,
further comprising a recording device that records the monitoring
image and the tomographic image in association with each other.
8. The optical tomographic imaging apparatus according to claim 1,
wherein said monitoring device comprises at least one of a camera,
an area sensor, and a confocal microscope.
9. The optical tomographic imaging apparatus according to claim 1,
further comprising an optical fiber forming at least one of the
following optical paths: an optical path that guides multiple beams
obtained from a light source or multiple beams emitted from
multiple light sources to a position at which the multiple beams
are split into the plurality of measuring beams and the plurality
of reference beams; an optical path that guides the plurality of
measuring beams to the subject's eye; an optical path that guides
the plurality of return beams to a photoelectric conversion
circuit; and an optical path that guides the plurality of reference
beams to the photoelectric conversion circuit.
10. (canceled)
11. A non-transitory computer-readable recording medium that has
the program that executes the method according to claim 12 recorded
thereon.
12. A method for taking an optical tomographic image by using the
optical tomographic imaging apparatus according to claim 5 to
thereby take a tomographic image of the subject's eye, the method
comprising: a first adjusting step of setting the scanning range to
be smaller than a predetermined imaging range; a second adjusting
step of using the monitoring device to monitor a state in which the
anterior eye part is irradiated with the plurality of measuring
beams; a third adjusting step of increasing/decreasing the number
of the plurality of measuring beams to recognize the relative
positions of the plurality of measuring beams and the subject's
eye; and a fourth adjusting step of using at least one of the face
fixation unit, a fixation lamp, and a measuring optical system to
adjust the relative positions of the plurality of measuring beams
and the subject's eye.
13. An optical tomographic imaging apparatus that obtains at least
a tomographic image of an subject's eye based on a plurality of
combined beams obtained by combining a plurality of return beams
from the subject's eye that is irradiated with a plurality of
measuring beams and a plurality of reference beams each of which
respectively correspond to each of the plurality of measuring
beams, the optical tomographic imaging apparatus comprising: an
irradiating device that irradiates an anterior eye part of the
subject's eye with the plurality of measuring beams; an obtaining
device that obtains information of the irradiated ranges where the
anterior eye part is irradiated with the plurality of measuring
beams by said irradiating device; and an adjusting device that
adjusts each of the irradiated ranges to be a predetermined
overlapped state based on the information of the irradiated
ranges.
14. The optical tomographic imaging apparatus according to claim
13, wherein the information of the irradiated ranges is information
of an overlapped area of the irradiated ranges, and said adjusting
device increases the overlapped area in order to adjust to the
predetermined overlapped state.
15. The optical tomographic imaging apparatus according to claim
13, wherein the information of the irradiated ranges is information
of a distance between an approximate center of the irradiated
ranges, and said adjusting device decreases the distance in order
to adjust to the predetermined overlapped state.
16. The optical tomographic imaging apparatus according to claim
13, wherein the predetermined overlapped state is a state that an
optical axis of the plurality of measuring beams intersect at an
approximate center of the anterior eye part of the subject's
eye.
17. The optical tomographic imaging apparatus according to claim
13, wherein said adjusting device comprises a distance shifting
device that shifts the distance between the irradiating device and
the anterior eye part of the subject's eye.
18. The optical tomographic imaging apparatus according to claim
13, wherein said obtaining device comprises a monitoring image
obtaining device that obtains a monitoring image of the anterior
eye part of the subject's eye, and said obtaining device obtains
information of the irradiated ranges by analyzing the monitoring
image.
Description
TECHNICAL FIELD
[0001] The present invention relates to an optical tomographic
imaging apparatus and an imaging method for an optical tomographic
image, and more particularly, to an optical tomographic imaging
apparatus and an imaging method for an optical tomographic image
that are used for ophthalmological care or the like.
BACKGROUND ART
[0002] Currently, there are various types of ophthalmological
instruments using an optical instrument.
[0003] For instance, as an optical instrument for monitoring an
eye, there are used various instruments such as an anterior eye
part imaging instrument, a fundus camera, a confocal laser scanning
ophthalmoscope (scanning laser ophthalmoscope: SLO), and the
like.
[0004] In particular, an optical tomographic imaging apparatus that
performs optical coherence tomography (OCT) utilizing an
interference phenomenon of multi-wavelength light is an apparatus
capable of obtaining a tomographic image of a sample with high
resolution.
[0005] For this reason, the optical tomographic imaging apparatus
is becoming an indispensable apparatus as an ophthalmological
instrument for a specialist of retina in the outpatient field.
Hereinbelow, the optical tomographic imaging apparatus is referred
to as an OCT apparatus.
[0006] In the above-mentioned OCT apparatus, a measuring beam that
is a low coherence beam is irradiated to a sample, and
backscattered light from the sample can be measured with high
sensitivity by using an interference system.
[0007] In addition, the OCT apparatus is capable of obtaining a
tomographic image with high resolution by scanning the sample with
the measuring beams.
[0008] This enables the OCT apparatus to image a tomographic image
of a retina in the fundus of an object eye with high resolution,
and hence the OCT apparatus is used widely for ophthalmological
diagnosis of retina or the like.
[0009] In recent years, the OCT apparatus for ophthalmological use
has been changing from a conventional time-domain method to a
Fourier-domain method by which faster imaging is possible.
High-speed imaging prevents blurring or missing of an image due to
eye movement such as involuntary eye movement.
[0010] However, even with the Fourier-domain method capable of
high-speed imaging, it is impossible to completely eliminate the
blurring or the missing of an image due to the eye movement. Hence,
further speed-up is desired.
[0011] In Japanese Patent Application Laid-Open No. 2006-195240, a
microlens array and a Nipkow disk are used to realize a multi-beam
OCT apparatus having multiple measuring beams. This OCT apparatus
enables obtaining a tomographic image and a fluorescence
tomographic image of a living body at high speed.
[0012] Japanese Patent No. 2,875,181 discloses an OCT apparatus
including multiple light sources, an object beam image forming
optical system provided in common for the multiple light sources,
and multiple photosensors discretely disposed at positions
corresponding to the positions of a reference beam image forming
optical system provided in common and light sources.
[0013] In this OCT apparatus, data is obtained simultaneously at
multiple points, and reference beams are shifted to obtain
multi-point data, which enables data to be obtained at high
speed.
[0014] Further, the OCT apparatus causes the measuring beams that
are low coherence beams to form an image at a predetermined
position of the retina, to thereby obtain a tomographic image.
[0015] However, there is a case where, due to a factor on the
object eye side, such as difficulty in making the object eye remain
at rest, it is difficult for the measuring beams to pass through
the pupil and form an image at the predetermined position of the
retina without being vignetted by the iris.
[0016] Specifically, in the OCT apparatus, if the measuring beams
are vignetted by the iris, a ratio of the measuring beams reaching
the predetermined position of the retina decreases, and
accordingly, beams reflected from the retina may decrease. In this
case, because there is an upper limit on power of the measuring
beams for a safety reason, the contrast of the tomographic image to
be obtained as a final result becomes low.
[0017] In particular, such a tendency becomes more conspicuous in a
case where the beam diameter of the measuring beam is made larger
so as to achieve an OCT apparatus having high resolution in a
direction perpendicular to the optical axis, or in a case where a
multi-beam OCT apparatus having multiple measuring beams is
configured so as to achieve a high-speed OCT apparatus.
[0018] Japanese Patent Application Laid-Open No. 2002-174769
discloses an OCT apparatus for monitoring the inside of a
biological sample, which is capable of high-resolution
monitoring.
[0019] In this OCT apparatus, at the time of monitoring a sample, a
beam diameter changing optical system is used to switch between a
mode that enables high-resolution monitoring and a mode that
enables wide-range monitoring, which therefore enables monitoring
with a high S/N ratio.
[0020] As described above, when the OCT apparatus is used to
monitor a fundus, there is a case where, due to a factor on the
object eye side, such as difficulty in making the object eye remain
at rest, it is difficult for the measuring beams to pass through
the pupil and form an image at the predetermined position of the
retina without irradiating the iris.
[0021] In particular, in a case where the multi-beam OCT apparatus
having multiple measuring beams is configured so as to obtain a
wide-range tomographic image at high speed, an influence thereof
becomes more conspicuous.
[0022] In Japanese Patent Application Laid-Open No. 2006-195240
described above, the microlens array and the Nipkow disk are used
to realize the multi-beam OCT apparatus, which is capable of
high-speed imaging. However, Japanese Patent Application Laid-Open
No. 2006-195240 gives no particular consideration to a measure
against the above-mentioned factor on the object eye side, that is,
the difficulty in making the object eye remain at rest, which is
necessary at the time of monitoring a fundus. In Japanese Patent
No. 2,875,181 described above, the OCT apparatus including the
multiple light sources and the multiple photosensors is realized to
enable high-speed imaging. However, Japanese Patent No. 2,875,181
also gives no particular consideration to a measure against the
above-mentioned factor on the object eye side, that is, the
difficulty in making the object eye remain at rest, which is
necessary at the time of monitoring a fundus.
[0023] In Japanese Patent Application Laid-Open No. 2002-174769
described above, the beam diameter changing optical system is used
to switch between the mode that enables high-resolution monitoring
and the mode that enables wide-range monitoring, which therefore
enables high-resolution monitoring.
[0024] However, Japanese Patent Application Laid-Open No.
2002-174769 also gives no particular consideration to a measure
against the above-mentioned factor on the object eye side, that is,
the difficulty in making the object eye remain at rest, which is
necessary at the time of monitoring a fundus.
DISCLOSURE OF THE INVENTION
[0025] In view of the above-mentioned problems, the present
invention has an object to provide an optical tomographic imaging
apparatus and an imaging method for an optical tomographic image,
which are capable of, when imaging a tomographic image of an
object, monitoring an incident state represented by an incident
position and an incident angle of a measuring beam group with
respect to the object, causing the measuring beam group to form an
image at a predetermined position of the object, and obtaining the
tomographic image at high speed.
[0026] The present invention provides an optical tomographic
imaging apparatus configured as follows. The optical tomographic
imaging apparatus is configured to:
[0027] split, multiple beams emitted from a light source or
multiple beams emitted from multiple light sources, into a
measuring beam group and a reference beam group, and guide the
measuring beam group and the reference beam group to an object and
a reference mirror, respectively; and
[0028] use a return beam group from the measuring beam group
reflected or scattered by the object, and the reference beam group
reflected by the reference mirror to image a tomographic image of
the object,
[0029] the optical tomographic imaging apparatus comprising a
monitoring device for obtaining a monitoring image of the
object,
[0030] the monitoring device being capable of monitoring an
incident state represented by an incident position and an incident
angle of the measuring beam group with respect to the object.
[0031] According to the present invention, when the tomographic
image of an object is imaged, the incident state represented by the
incident position and the incident angle of the measuring beam
group with respect to the object may be monitored, the measuring
beam group may be caused to form an image at the predetermined
position of the object, and the tomographic image may be obtained
at high speed.
[0032] Further features of the present invention will become
apparent from the following description of exemplary embodiments
with reference to the attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0033] FIG. 1 is a diagram illustrating a configuration of an
optical system of an OCT apparatus according to a first embodiment
of the present invention.
[0034] FIGS. 2A, 2B, 2C, and 2D are diagrams for describing a
method of obtaining a tomographic image by the OCT apparatus
according to the first embodiment of the present invention.
[0035] FIGS. 3A and 3B are diagrams for describing a configuration
of a measuring beam monitoring system of the OCT apparatus
according to the first embodiment of the present invention.
[0036] FIGS. 4A, 4B, and 4C are diagrams for describing the
configuration of the measuring beam monitoring system of the OCT
apparatus according to the first embodiment of the present
invention.
[0037] FIGS. 5A, 5B, and 5C are diagrams for describing the
configuration of the measuring beam monitoring system of the OCT
apparatus according to the first embodiment of the present
invention.
[0038] FIGS. 6A and 6B are diagrams for describing the
configuration of the measuring beam monitoring system of the OCT
apparatus according to the first embodiment of the present
invention.
[0039] FIGS. 7A, 7B, 7C, and 7D are diagrams for describing a
method of adjusting a position of an object eye by the OCT
apparatus according to the first embodiment of the present
invention.
[0040] FIG. 8 is a flow chart of respective processes for
describing a method of imaging an optical tomographic image
according to the first embodiment of the present invention.
[0041] FIG. 9 is a diagram illustrating an overall configuration of
an OCT apparatus according to a second embodiment of the present
invention.
[0042] FIG. 10 is a diagram illustrating a configuration of an
optical system of the OCT apparatus according to the second
embodiment of the present invention.
[0043] FIG. 11 is a diagram illustrating a configuration of an OCT
imaging portion of the OCT apparatus according to the second
embodiment of the present invention.
BEST MODE FOR CARRYING OUT THE INVENTION
[0044] Hereinbelow, an embodiment mode of the present invention is
described.
[0045] In this embodiment mode, the above-mentioned configuration
of the present invention may be applied to thereby configure, for
example, the optical tomographic imaging apparatus (OCT apparatus)
as described in the following (1) to (20).
[0046] (1) As illustrated in FIG. 1, the optical tomographic
imaging apparatus according to this embodiment mode is configured
to: further split beams that have been emitted from a light source
101 and split into multiple beams, into a measuring beam group
106-1 to 106-3 and a reference beam group 105-1 to 105-3, the
measuring beam group and the reference beam group including the
split multiple beams; guide the measuring beam group and the
reference beam group to an object 107 and a reference mirror 114,
respectively; and use a return beam group 108-1 to 108-3 obtained
from the measuring beam group reflected or scattered by the object,
and the reference beam group reflected by the reference mirror to
image a tomographic image (see FIG. 2C) of the object.
[0047] On this occasion, the optical tomographic imaging apparatus
includes a monitoring device 157 for obtaining a monitoring image
of the object, and the monitoring device is capable of monitoring
an incident state represented by an incident position and an
incident angle of the measuring beam group with respect to the
object.
[0048] With this configuration, an optical tomographic imaging
apparatus 100 including the measuring beam group constituted of
multiple measuring beams monitors a state in which the object is
irradiated with the measuring beam group.
[0049] As described above, with a configuration in which the
optical tomographic imaging apparatus includes the monitoring
device for obtaining a monitoring image, the state in which the
object is irradiated with the measuring beam group may be
recognized with ease.
[0050] As a result, positional relation between the measuring beam
group and the object may be optimized with ease, enabling a
wide-range tomographic image to be obtained at high speed.
[0051] (2) With a configuration in which the optical tomographic
imaging apparatus includes a position recognizing device for
recognizing the incident position of the measuring beam group based
on the monitoring image obtained by the monitoring device, relative
positions of the measuring beam group and the object may be
recognized with ease, resulting in easier adjustment of the
relative positions.
[0052] (3) With a configuration in which the monitoring device is
disposed in proximity of an object eye that is the object, and is
capable of monitoring a state in which an anterior eye part of the
object eye is irradiated with the measuring beam group, the
measuring beam group may enter the object eye in an optically
optimal state.
[0053] (4) With a configuration in which the optical tomographic
imaging apparatus includes an adjusting device (personal computer
125) capable of adjusting the relative positions of the measuring
beam group and the object eye based on the monitoring image
obtained by the monitoring device, the measuring beam group may
enter the object eye optically appropriately.
[0054] (5) With a configuration in which the adjusting device is
capable of adjusting an area of the anterior eye part, which is
irradiated with the measuring beam group, to a minimum, the
measuring beam group may enter the object eye optically
appropriately.
[0055] (6) With a configuration in which the adjusting device is
capable of increasing and decreasing a number of beams of the
measuring beam group, an indicator for determining whether or not
the relative positions of the measuring beam group and the object
eye are closer to each other compared to optimal positions may be
obtained.
[0056] (7) With a configuration in which a beam number
increasing/decreasing device for the measuring beam group increases
and decreases the number of beams of the measuring beam group to
recognize the relative positions of the measuring beam group and
the object eye, an indicator for determining how adjustment is made
by using the adjustment device may be obtained.
[0057] (8) With a configuration in which the adjusting device is
capable of increasing and decreasing a scanning range of the
measuring beam group, the scanning range of the measuring beam
group at the time of adjusting the relative positions of the
measuring beam group and the object eye may be reduced, resulting
in easier adjustment.
[0058] (9) With a configuration in which the adjusting device is
capable of shifting a gaze with use of a fixation target (e.g. a
fixation lamp) at which the object eye is to be guided, rotational
movement of the object eye may be prompted, mainly. As a result,
the measuring beam group may be caused to form an image at a
predetermined position of a retina with ease.
[0059] (10) With a configuration in which the adjusting device is
capable of shifting a face fixation unit for supporting a face of
an examinee at a predetermined position, parallel shift of the
object eye is enabled. As a result, the measuring beam group may be
caused to form an image at the predetermined position of the retina
with ease.
[0060] (11) With a configuration in which the adjusting device is
capable of adjusting a measuring optical system for guiding the
measuring beam group to the object, the measuring beam group may be
adjusted so as to enter the object appropriately.
[0061] (12) With a configuration in which the optical tomographic
imaging apparatus includes a recording device for recording the
monitoring image and the tomographic image in association with each
other, the state in which the measuring beam group enters the
object may be recognized, which therefore allows discussion on the
reliability of the obtained tomographic image.
[0062] (13) With a configuration in which the monitoring device
includes a camera 157, the state in which the measuring beam group
enters the anterior eye part may be monitored with ease.
[0063] (14) With a configuration in which the monitoring device
includes an area sensor (see 501 of FIG. 10), the state in which
the measuring beam group enters the anterior eye part may be
monitored with ease.
[0064] (15) With a configuration in which the monitoring device
includes a confocal microscope, the state in which the measuring
beams enter the anterior eye part may be monitored with ease.
[0065] (16) With a configuration in which the optical tomographic
imaging apparatus includes an optical fiber forming at least one of
the following optical paths, a compact optical tomographic imaging
apparatus that is excellent in stability may be realized: an
optical path for guiding the multiple beams obtained from the light
source or the multiple beams emitted from the multiple light
sources to a position at which the multiple beams are split into
the measuring beam group and the reference beam group; an optical
path for guiding the measuring beam group to the object; an optical
path for guiding the return beam group to a photoelectric
conversion circuit; and an optical path for guiding the reference
beam group to the photoelectric conversion circuit.
[0066] (17) With a configuration in which the optical tomographic
imaging apparatus for imaging a tomographic image of a fundus of
the object eye includes a fundus camera main body portion 300 and a
camera portion 500 for imaging a plane image of the fundus of the
object eye, an apparatus having both functions of a fundus camera
and an OCT apparatus may be realized.
[0067] Accordingly, an OCT apparatus with high space use efficiency
and high profitability may be realized.
[0068] (18) With a configuration in which the fundus camera main
body portion and the camera portion for imaging a plane image of
the fundus are connectable to each other via an adapter 400, the
function of the OCT apparatus may be realized by using an existing
fundus camera.
[0069] (19) In the optical tomographic imaging apparatus described
in any one of the above items (1) to (18), there is employed an
imaging method for an optical tomographic image, in which a
tomographic image of the object is imaged, including:
[0070] a first adjusting step of using a scanning range
increasing/decreasing device to set the scanning range to be
smaller than a desired imaging range;
[0071] a second adjusting step of using the monitoring device to
monitor the state in which the anterior eye part is irradiated with
the measuring beam group;
[0072] a third adjusting step of using the beam number
increasing/decreasing device to recognize the relative positions of
the measuring beam group and the object eye; and
[0073] a fourth adjusting step of using at least one of the face
fixation unit, the fixation lamp, and the measuring optical system
to adjust the relative positions of the measuring beam group and
the object eye. As a result, the measuring beam group may be
efficiently caused to form an image at the predetermined position
of the retina of the object eye, resulting in efficient
imaging.
[0074] (20) By automatically performing at least one of the first
to fourth steps described above, the relative positions of the
measuring beam group and the object eye may be efficiently
adjusted.
EMBODIMENTS
[0075] Next, embodiments of the present invention are
described.
First Embodiment
[0076] In a first embodiment, an OCT apparatus to which the present
invention is applied is described. In this embodiment, in
particular, an apparatus for imaging a tomographic image (OCT
image) of an object eye is described.
[0077] The OCT apparatus described in this embodiment is a
Fourier-domain OCT apparatus (Fourier Domain OCT), and is also a
multi-beam OCT apparatus that has three measuring beams for fast
imaging and is capable of obtaining three tomographic images
simultaneously.
[0078] In this embodiment, the case where the OCT apparatus has
three measuring beams is described, but the number of measuring
beams may be increased depending on a predetermined imaging
speed.
[0079] First, an overall schematic configuration of an optical
system of the OCT apparatus according to this embodiment is
described.
[0080] FIG. 1 is a diagram illustrating the overall schematic
configuration of the optical system of the OCT apparatus according
to this embodiment.
[0081] In FIG. 1, the OCT apparatus is represented by 100; a light
source, 101; an emitted beam, 104; reference beams, 105-1, 105-2,
and 105-3; measuring beams, 106-1, 106-2, and 106-3; multiplexed
beams, 142-1, 142-2, and 142-3; the object eye, 107; return beams,
108-1, 108-2, and 108-3; a single mode fiber, 110; lenses, 120-1,
120-2, 120-3, 135-1, 135-2, 135-3, and 135-4; and a mirror, 114.
Dispersion compensation glass is represented by 115; electrical
stages, 117-1 and 117-2; an XY scanner, 119; and a personal
computer, 125.
[0082] A cornea is represented by 126; a retina, 127; optical
couplers, 131-1, 131-2, 131-3, and 156; a line camera, 139; a frame
grabber, 140; a transmission grating, 141; polarization
controllers, 153-1, 153-2, 153-3, and 153-4; fiber length adjusting
devices, 155-1, 155-2, and 155-3; and a monitoring camera, 157.
[0083] As illustrated in FIG. 1, the OCT apparatus 100 of this
embodiment forms a Michelson interference system as a whole.
[0084] In FIG. 1, the emitted beam 104 that is a beam emitted from
the light source 101 is split by the optical coupler 156 into three
emitted beams 104-1, 104-2, and 104-3. In this embodiment, a beam
emitted from one light source is split into multiple beams to
obtain multiple emitted beams. However, multiple light sources may
be prepared to obtain multiple emitted beams.
[0085] Further, the emitted beams 104-1, 104-2, and 104-3 pass
through the polarization controller 153-1, and are split, by the
optical couplers 131-1, 131-2, and 131-3, into the reference beams
105-1, 105-2, and 105-3 and the measuring beams 106-1, 106-2, and
106-3, respectively, with an intensity ratio of 50:50.
[0086] The measuring beams 106-1, 106-2, and 106-3 are returned as
the return beams 108-1, 108-2, and 108-3 that have been reflected
or scattered by the retina 127 of the object eye 107 to be
monitored. Then, the return beams 108-1, 108-2, and 108-3 are
multiplexed with the reference beams 105-1, 105-2, and 105-3 by the
optical couplers 131-1, 131-2, and 131-3.
[0087] After the reference beams 105-1, 105-2, and 105-3 and the
return beams 108-1, 108-2, and 108-3 are multiplexed with each
other, the resultant beams are dispersed according to the
wavelengths by the transmission gratings 141, and input to the line
camera 139. The line camera 139 converts a light intensity into a
voltage for each position (wavelength), and the tomographic image
of the object eye 107 is generated by using the voltage
signals.
[0088] Next, the light source 101 and matters relevant thereto are
described.
[0089] The light source 101 is a super luminescent diode (SLD),
which is a typical low coherence light source.
[0090] The light source 101 has a wavelength of 830 nm and a
bandwidth of 50 nm. Here, the bandwidth is an important parameter
because the bandwidth affects the resolution of the obtained
tomographic image in the optical axis direction.
[0091] In addition, the light source of an SLD type is used in this
embodiment, but an amplified spontaneous emission (ASE) type or the
like may also be used as long as the light source emits a low
coherence beam. In addition, concerning the wavelength of light,
near-infrared light is suitable because the light is used for
measuring an eye.
[0092] Further, because the wavelength affects the resolution of
the obtained tomographic image in the lateral direction, the
wavelength is desirably as short as possible. Here, the wavelength
is 830 nm. Depending on the measurement site to be monitored,
another wavelength may be selected.
[0093] Next, optical paths of the reference beams 105-1, 105-2, and
105-3 are described.
[0094] The reference beams 105-1, 105-2, and 105-3 split by the
optical couplers 131-1, 131-2, and 131-3 pass through the
polarization controller 153-2, and the fiber length adjusting
devices 155-1, 155-2, and 155-3. Then, the resultant beams are
converted into parallel beams having a beam diameter of 1 mm by the
lenses 135-1, and are then emitted.
[0095] Next, the reference beams 105-1, 105-2, and 105-3 pass
through the dispersion compensation glass 115, and are condensed
onto the mirror 114 by the lenses 135-2.
[0096] Next, the reference beams 105-1, 105-2, and 105-3 change the
direction at the mirror 114, and are guided toward the optical
couplers 131-1, 131-2, and 131-3 again.
[0097] Next, the reference beams 105-1, 105-2, and 105-3 pass
through the optical couplers 131-1, 131-2, and 131-3, and are
guided to the line camera 139.
[0098] Here, the dispersion compensation glass 115 compensates for
dispersion that occurs when the measuring beams 106-1, 106-2, and
106-3 enter the object eye 107 and are reflected thereby, with
respect to the reference beams 105-1, 105-2, and 105-3,
respectively.
[0099] Here, assuming a value typical as an average diameter of the
eyeball of Japanese people, L is set to 23 mm.
[0100] Further, the electrical stage 117-1 is capable of moving in
directions indicated by arrows in the figure, which enables
adjusting and controlling the optical path lengths of the reference
beams 105-1, 105-2, and 105-3.
[0101] In addition, the electrical stage 117-1 may be controlled by
the personal computer 125 at high speed.
[0102] Further, the fiber length adjusting devices 155-1, 155-2,
and 155-3 are installed for the purpose of making fine adjustment
on the respective fiber lengths, and are capable of adjusting the
optical path lengths of the reference beams 105-1, 105-2, and 105-3
according to the respective measurement sites of the measuring
beams 106-1, 106-2, and 106-3. The personal computer 125 may
control the fiber length adjusting devices 155-1, 155-2, and
155-3.
[0103] Next, the optical paths of the measuring beams 106-1, 106-2,
and 106-3 are described.
[0104] The measuring beams 106-1, 106-2, and 106-3 split by the
optical couplers 131-1, 131-2, and 131-3 pass through the
polarization controller 153-4, and are emitted as parallel beams
having a beam diameter of 1 mm by the lens 120-3. The resultant
beams are input to a mirror of the XY scanner 119.
[0105] Here, the XY scanner 119 is described as a single mirror for
simple description, but actually, two mirrors of an X scan mirror
and a Y scan mirror are disposed closely to each other so as to
raster-scan the retina 127 in the direction perpendicular to the
optical axis. Further, the lenses 120-1 and 120-3 are adjusted so
that the center of each of the measuring beams 106-1, 106-2, and
106-3 is aligned with the rotation center of the mirror of the XY
scanner 119.
[0106] The lenses 120-1 and 120-2, which constitute an optical
system for scanning the retina 127 with the measuring beams 106-1,
106-2, and 106-3, have a role of scanning the retina 127 with the
measuring beams 106-1, 106-2, and 106-3, with the vicinity of the
cornea 126 set as a supporting point.
[0107] Here, focal lengths of the lenses 120-1 and 120-2 are 50 mm
each.
[0108] Further, the electrical stage 117-2 is capable of moving in
directions indicated by arrows, which enables adjusting and
controlling the position of the lens 120-2 attached thereto. By
adjusting the position of the lens 120-2, the measuring beams
106-1, 106-2, and 106-3 may be condensed at a specific layer of the
retina 127 of the object eye 107 for monitoring.
[0109] Further, a case of the object eye 107 having a refractive
error may also be handled. When the measuring beams 106-1, 106-2,
and 106-3 enter the object eye 107, the measuring beams 106-1,
106-2, and 106-3 are reflected or scattered by the retina 127 to
become the return beams 108-1, 108-2, and 108-3. Then, the return
beams 108-1, 108-2, and 108-3 pass through the optical couplers
131-1, 131-2, and 131-3 to be guided to the line camera 139.
[0110] Here, the electrical stage 117-2 can be controlled by the
personal computer 125 at high speed.
[0111] Next, a configuration of a measurement system of the OCT
apparatus according to this embodiment is described.
[0112] The return beams 108-1, 108-2, and 108-3, which are beams
reflected or scattered by the retina 127, and the reference beams
105-1, 105-2, and 105-3 are multiplexed with each other by the
optical couplers 131-1, 131-2, and 131-3, respectively.
[0113] Then, the multiplexed beams 142-1, 142-2, and 142-3 are
dispersed according to the wavelengths by the transmission gratings
141, and condensed by the lenses 135-3. Then, the intensity of
light is converted into voltage for each position (wavelength) by
the line camera 139.
[0114] Specifically, in association with the number of the
measuring beams 106-1, 106-2, and 106-3, the line camera 139
monitors interference patterns of spectral regions along three
wavelength axes.
[0115] A voltage signal group thus obtained is converted into
digital values by the frame grabber 140. After that, the personal
computer 125 performs data processing to form a tomographic
image.
[0116] Here, the line camera 139 has 4,096 pixels, and uses 3,072
pixels thereof to obtain the intensity of the multiplexed beams
142-1, 142-2, and 142-3 for each of the wavelengths (divided into
1,024 positions).
[0117] Next, a method of obtaining a tomographic image by using the
OCT apparatus is described.
[0118] Here, the method of obtaining a tomographic image (surface
parallel to the optical axis) of the retina 127 is described with
reference to FIGS. 2A, 2B, 2C, and 2D. Components identical to or
corresponding to the components illustrated in FIG. 1 are denoted
by the same reference numerals, and hence repetitive description
thereof is omitted.
[0119] FIG. 2A illustrates a state in which the object eye 107 is
monitored by the OCT apparatus 100.
[0120] As illustrated in FIG. 2A, the measuring beams 106-1, 106-2,
and 106-3 pass through the cornea 126, enter the retina 127, and
are reflected or scattered at various positions to become the
return beams 108-1, 108-2, and 108-3. The return beams 108-1,
108-2, and 108-3 reach the line camera 139 with time delays
corresponding to the respective positions.
[0121] Here, the bandwidth of the light source 101 is wide, and a
spatial coherence length thereof is short. Therefore, if an optical
path length for the reference beam path is substantially equal to
an optical path length for the measuring beam path, the line camera
139 may detect the interference pattern. As described above, the
line camera 139 obtains the interference pattern of the spectral
region along the wavelength axis.
[0122] Next, considering characteristics of the line camera 139 and
the transmission grating 141, the interference pattern, which is
information along the wavelength axis, is converted into an
interference pattern along an optical frequency axis for each of
the multiplexed beams 142-1, 142-2, and 142-3.
[0123] Further, the converted interference pattern along the
optical frequency axis is subjected to inverse Fourier transform so
as to obtain information regarding a depth direction.
[0124] Further, for the sake of convenience, of the measuring
beams, only the measuring beam 106-2 is illustrated in FIG. 2B. As
illustrated in FIG. 2B, if the interference pattern is detected by
driving the X-axis of the XY scanner 119, the interference pattern
may be obtained for each position of the X-axis. In other words,
information on the depth direction may be obtained for each
position of the X-axis.
[0125] As a result, a two-dimensional distribution of intensities
of the return beam 108-2 may be obtained with regard to an X-Z
plane. FIG. 2C illustrates a tomographic image 132 thus
obtained.
[0126] Inherently, the tomographic image 132 is constituted of
intensities of the return beams 108 arranged in an array as
described above, and is displayed as, for example, a gray scale
image corresponding to the intensities. In FIG. 2C, only boundaries
of the obtained tomographic image are emphasized and displayed.
[0127] Further, as illustrated in FIG. 2D, by controlling the XY
scanner 119 to raster-scan the retina 127 with the measuring beams
106-1, 106-2, and 106-3, three tomographic images may be obtained
simultaneously and successively. Here, the scanning is performed
with a main scanning direction of the XY scanner 119 set as an
X-axis direction and a sub-scanning direction thereof set as a
Y-axis direction. As a result, multiple Y-Z plane tomographic
images may be obtained. Note that, though a case where the
measuring beams 106-1, 106-2, and 106-3 perform scanning without
overlapping one another is described herein, overlapping scanning
may also be performed for a purpose of registration of a
tomographic image.
[0128] Next, with reference to FIG. 1, a configuration of a
measuring beam monitoring system, which is a feature of the present
invention, is described.
[0129] In the OCT apparatus 100, as described above, the measuring
beams 106-1, 106-2, and 106-3 pass through the cornea 126, and
then, the retina 127 is irradiated therewith. The monitoring camera
157 is installed for the purpose of monitoring a state in which the
measuring beams 106-1, 106-2, and 106-3 pass through the cornea 126
and enter the retina 127.
[0130] Here, the monitoring camera 157 is installed on a right
forward side of the object eye 107. However, as long as the
monitoring camera 157 may monitor the vicinity of the cornea 126,
the monitoring camera 157 may be located anywhere.
[0131] Further, by utilizing a monitoring image obtained by the
monitoring device, an adjusting device configured so that relative
positions of a measuring beam group and the object eye can be
adjusted by the device may be configured as follows.
[0132] For example, with the monitoring camera 157 and the personal
computer 125 electrically connected, the monitoring image obtained
by the monitoring camera 157 is captured by the personal computer
125, is subjected to image processing or the like, and is used to
adjust the relative positions of the OCT apparatus 100 and the
object eye 107.
[0133] Further, the monitoring image may be displayed and stored in
association with an OCT image. Here, in consideration of the
wavelength of the measuring beams 106-1, 106-2, and 106-3, which is
830 nm, a near-infrared camera is used for the monitoring camera
157. Further, the near-infrared camera may be configured by
combining a near-infrared area sensor and a lens.
[0134] Next, with reference to FIGS. 3A and 3B, FIGS. 4A, 4B, and
4C, FIGS. 5A, 5B, and 5C, and FIGS. 6A and 6B, a monitoring image
144 obtained using the monitoring camera 157 is described.
[0135] Components identical or corresponding to the components
illustrated in FIGS. 1, 2A, 2B, 2C, and 2D are denoted by the same
reference numerals, and hence repetitive description thereof is
omitted.
[0136] FIG. 3A is a schematic diagram 143 schematically
illustrating a cross section of the object eye 107, which is a
monitoring target.
[0137] Here, a pupil is represented by 158; an iris, 159; and a
crystalline lens, 160. FIG. 3B illustrates the monitoring image
144.
[0138] Here, a state in which the object eye 107 is appropriately
irradiated with the measuring beams 106-1, 106-2, and 106-3 is
described.
[0139] Specifically, appropriate irradiation means a state in which
the relative positions of the object eye 107 and the OCT apparatus
100 are adjusted so that the measuring beams 106-1, 106-2, and
106-3 pass through the pupil 158 without being vignetted by the
iris 159, and that the measuring beams intersect in the vicinity of
a surface of the crystalline lens 160.
[0140] Because the pupil 158 is the narrowest part in the optical
paths of the measuring beams 106-1, 106-2, and 106-3, by adjusting
an irradiation position according to the size of the pupil 158 as
described above, wider measuring beams 106-1, 106-2, and 106-3 may
be input onto the object eye 107, which is advantageous for
achieving a higher resolution of the OCT apparatus 100.
[0141] FIG. 3B illustrates the monitoring image 144 for monitoring
a state of the measuring beams 106-1, 106-2, and 106-3, with a
focal point thereof adjusted to the vicinity of the surface of the
crystalline lens 160.
[0142] Here, because the measuring beams 106-1, 106-2, and 106-3
pass through substantially the same position, the measuring beams
106-1, 106-2, and 106-3 are apparently recognized as one
circle.
[0143] Here, a distance between the surface of the crystalline lens
160 and the lens 120-2 is 50 mm, which is equal to a focal length
of the lens 120-2, hence aA mirror surface of the XY scanner 119
and the surface of the crystalline lens 160 have an optically
conjugate relationship.
[0144] Next, a case where the relative positions of the object eye
107 and the OCT apparatus 100 are not appropriate is described.
[0145] FIGS. 4A and 4B illustrate a case where the relative
positions of the object eye 107 and the OCT apparatus 100 are
closer to each other compared to optimal positions illustrated in
FIG. 3A.
[0146] In this case, as can be seen in FIG. 4A, the measuring beams
106-1, 106-2, and 106-3 are monitored as being located in a wider
area apparently as also illustrated in FIG. 4B.
[0147] Here, if the measuring beam 106-1 is shielded, a monitoring
image 144 as illustrated in FIG. 4C is obtained, in which the
measuring beams 106-2 and 106-3 are monitored in a +X direction
compared to the case before shielding. Thus, it is understood that
the relative positions of the object eye 107 and the OCT apparatus
100 are closer to each other compared to the optimal positions.
[0148] Further, as illustrated in FIG. 5A, in a case where the
relative positions of the object eye 107 and the OCT apparatus 100
are distant from each other compared to the optimal positions
illustrated in FIG. 3A, an monitoring image 144 as illustrated in
FIG. 5B is obtained.
[0149] Similarly, if the measuring beam 106-1 is shielded, the
monitoring image 144 as illustrated in FIG. 5C is obtained, in
which the measuring beams 106-2 and 106-3 are monitored in a -X
direction. Thus, it is understood that the relative positions of
the object eye 107 and the OCT apparatus 100 are distant from each
other compared to the optimal positions.
[0150] Further, as illustrated in FIG. 6A, in a case where the
object eye 107 is displaced in the -X direction with respect to the
OCT apparatus 100, a monitoring image 144 as illustrated in FIG. 6B
is obtained, clearly indicating the above-mentioned situation.
[0151] As described above, in the cases where the relative
positions of the object eye 107 and the OCT apparatus 100 are not
appropriate, the above-mentioned optically conjugate relationship
between the mirror surface of the XY scanner 119 and the surface of
the crystalline lens 160 does not hold.
[0152] Accordingly, in states typified by FIGS. 4A, 5A, and 6A, the
intensities of the return beams 108-1, 108-2, and 108-3 become
smaller compared to the state of FIG. 3A. As a result, a S/N ratio
of an interference signal for forming a tomographic image, which is
described later, becomes lower.
[0153] In general, there is an upper limit for the energy of a
measuring beam with which the retina is irradiated. Hence, in order
to obtain a tomographic image suitable for diagnosis, it is
important to input the measuring beams 106-1, 106-2, and 106-3 to
the pupil 158 appropriately. Further, due to such a reason as being
difficult to make an examinee remain at rest, even if the measuring
beams 106-1, 106-2, and 106-3 unintentionally irradiate the iris
159, the monitoring image 144 may be used as means for assessing
reliability of the obtained tomographic image.
[0154] Next, referring mainly to FIGS. 7A, 7B, 7C, and 7D, an
imaging method for an optical tomographic image, including
adjusting the position of the object eye and imaging the optical
tomographic image, which is a feature of the present invention, is
described in detail.
[0155] Components identical to or corresponding to the components
illustrated in FIG. 1, FIGS. 2A to 2D, FIGS. 3A and 3B, FIGS. 4A to
4C, FIGS. 5A to 5C, and FIGS. 6A and 6B are denoted by the same
reference numerals, and hence repetitive description thereof is
omitted.
[0156] In general, when the retina of the fundus is monitored, in
consideration of safety, scanning is performed over the retina with
measuring beams. The imaging method for an optical tomographic
image according to this embodiment is performed by scanning the
retina with the measuring beams, and a scanning range may be
adjusted as necessary.
[0157] In the imaging method for an optical tomographic image, for
example, the following processes of (1) to (4) are performed
successively. Alternatively, the processes may be performed again
after a while as necessary.
[0158] Further, by using a computer or the like, the following
processes may be automatically performed.
[0159] FIG. 8 is a flow chart of the respective processes for
describing the method of imaging an optical tomographic image.
[0160] (1) The object eye 107 of the examinee is guided to a
predetermined position, and then, the surface portion of the
crystalline lens 160 is monitored by using the monitoring camera
157 (see FIG. 1) to obtain a monitoring image 144. Here, it is
desired that the scanning range of the measuring beam be set to a
relatively small range (FIG. 7A).
[0161] (2) The measuring beam 106-1 is temporarily shielded to
obtain a monitoring image 144 (FIG. 7B). In the monitoring image
144, the measuring beams 106-2 and 106-3 are monitored on the side
of the +X direction. Accordingly, the position of the object eye
107 is assumed to be as illustrated in FIG. 7C. Further, by using
the personal computer 125, the monitoring image 144 may be
subjected to image processing to quantify the intensities of the
measuring beams 106-1, 106-2, and 106-3.
[0162] (3) By using a face fixation unit (not shown) or a fixation
lamp (not shown), the object eye 107 is guided in the +X direction
and in a +Z direction. By viewing the monitoring image 144,
guidance and adjustment are appropriately made so that the
measuring beams 106-1, 106-2, and 106-3 generate a minimum circle
in appearance, and are located at the center of the pupil 158 (FIG.
7D).
[0163] (4) The scanning range of the measuring beams is set to a
predetermined range. By adjusting the position of the lens 120-2,
diopter correction is performed so that the tomographic image
becomes clearer.
Second Embodiment
[0164] In a second embodiment, an OCT apparatus to which the
present invention applied is described.
[0165] In this embodiment, in particular, an apparatus for imaging
a tomographic image (OCT image) and a fundus image (plane image) of
an object eye is described.
[0166] In this embodiment, an OCT apparatus including an OCT
imaging portion connected to a fundus camera via an adapter is
described.
[0167] This embodiment describes an OCT apparatus with high space
use efficiency and high profitability. Similarly to the first
embodiment, the OCT apparatus described in this embodiment is an
OCT apparatus of a Fourier-domain method, and is also a multi-beam
OCT apparatus that has three measuring beams for fast imaging and
is capable of obtaining three tomographic images
simultaneously.
[0168] With reference to FIG. 9, an overall configuration of the
OCT apparatus including the adapter of this embodiment is
described. FIG. 9 is a side view of the OCT apparatus. An OCT
apparatus 200 includes an OCT imaging portion 102, a fundus camera
main body portion 300, an adapter 400, and a camera portion
500.
[0169] Here, the fundus camera main body portion 300, the adapter
400, and the camera portion 500 are optically connected to each
other.
[0170] Here, the fundus camera main body portion 300 and the
adapter 400 are supported so as to be relatively movable.
[0171] Therefore, optical adjustment may be performed roughly. In
addition, the adapter 400 and the OCT imaging portion 102 are
optically connected to each other via three single mode fibers 148.
The adapter 400 and the OCT imaging portion 102 have three
connectors 410 and three connectors 154, respectively. Therefore,
the adapter 400 and the OCT imaging portion 102 are easily
attachable to and detachable from each other. Further, a face
fixation unit 323 fixes a chin and a forehead of an examinee so
that the object eye is fixed for imaging.
[0172] Further, a personal computer 125 is used for creating and
displaying the tomographic image.
[0173] Here, as the camera portion 500, a general-purpose digital
single-lens reflex camera is used. The camera portion 500 is
connected to the adapter 400 or the fundus camera main body portion
300 via a general-purpose camera mount.
[0174] Next, with reference to FIG. 10, a configuration of an
optical system of the OCT apparatus including the adapter according
to this embodiment is described.
[0175] In FIG. 10, the OCT apparatus 200 for measuring the object
eye 107 includes the fundus camera main body portion 300, the
adapter 400, the camera portion 500, and the OCT imaging portion
102. The OCT apparatus 200 is intended to obtain a tomographic
image (OCT image) and a fundus image (plane image) of the retina
127 of the object eye 107 by using the OCT imaging portion 102 and
the camera portion 500.
[0176] First, the fundus camera main body portion 300 is
described.
[0177] An objective lens 302 is disposed so as to be opposed to the
object eye 107, and, on the optical axis thereof, a perforated
mirror 303 splits the optical path into an optical path 351 and an
optical path 352.
[0178] The optical path 352 forms an illuminating optical system
for illuminating the fundus of the object eye 107. In a lower
portion of the fundus camera main body portion 300, there are
disposed a halogen lamp 316 that is used for positioning the object
eye 107, and a strobe tube 314 that is used for imaging the fundus
of the object eye 107.
[0179] The fundus camera main body portion 300 further includes
condenser lenses 313 and 315 and a mirror 317. Illuminating light
emitted from the halogen lamp 316 and the strobe tube 314 is shaped
into a ring-like light flux by a ring slit 312 and is reflected by
the perforated mirror 303 so as to illuminate the fundus of the
object eye 107.
[0180] The fundus camera main body portion 300 further includes
lenses 309 and 311 and an optical filter 310.
[0181] The optical path 351 forms an imaging optical system for
imaging the tomographic image and the fundus image of the fundus of
the object eye 107. A focus lens 304 and an imaging lens 305 are
disposed on the right side of the perforated mirror 303.
[0182] Here, the focus lens 304 is supported so as to be movable in
the optical axis direction, and the personal computer 125 may
control the position thereof. Next, the optical path 351 is guided
to a fixation lamp 320 and a monitoring camera 321 via a quick
return mirror 318.
[0183] Here, the quick return mirror 318 is designed to reflect and
transmit a part of infrared light and to reflect visible light.
Because the quick return mirror 318 is designed to reflect and
transmit a part of infrared light, the fixation lamp 320, the
monitoring camera 321, and the OCT imaging portion 102 may be used
simultaneously.
[0184] In addition, a dichroic mirror 319 is designed to guide
visible light in the direction to the fixation lamp 320 and guide
infrared light in the direction to the monitoring camera 321.
[0185] Next, the optical path 351 is guided to the adapter 400 via
a mirror 306, a field lens 322, a mirror 307, and a relay lens
308.
[0186] Here, the monitoring camera 321 monitors the vicinity of the
cornea 126, which enables understanding a state in which the
measuring beams 106-1, 106-2, and 106-3 enter the object eye 107,
which is a characteristic of the present invention. In addition,
with the use of the fixation lamp 320, the object eye 127 may be
guided.
[0187] Next, a configuration of the optical system (adapter and
camera portion) is described.
[0188] The largest function of the adapter 400 is to split the
optical path 351 into an optical path 351-1 for imaging the
tomographic image and an optical path 351-2 for imaging the fundus
image via the dichroic mirror 405.
[0189] The adapter 400 further includes relay lenses 406 and 407,
an XY scanner 408, and a collimator lens 409.
[0190] Further, here, the relay lenses 406 and 407 are supported in
a movable manner so that the optical axis may be adjusted between
the optical paths 351-1 and 351-2 by fine positional
adjustment.
[0191] In addition, in FIG. 10, the XY scanner 408 is illustrated
as a single mirror for simple description, but, actually, two
mirrors of an X scan mirror and a Y scan mirror are disposed to be
close to each other so as to raster-scan the retina 127 in the
direction perpendicular to the optical axis.
[0192] In addition, the XY scanner 408 is controlled by the
personal computer 125.
[0193] In addition, the optical axis of the optical path 351-1 is
aligned with the rotation center of the two mirrors of the XY
scanner 408.
[0194] In addition, with the use of the three connectors 410 for
attaching three optical fibers, three measuring beams may be input
from the OCT imaging portion 102 to the adapter 400, the fundus
camera main body portion 300, and the object eye 107 in the stated
order.
[0195] The camera portion 500 is a digital single-lens reflex
camera for imaging the fundus image. The adapter 400 and the camera
portion 500 are connected to each other via a general-purpose
camera mount.
[0196] Hence, the adapter 400 and the camera portion 500 are easily
attachable to and detachable from each other. The fundus image is
generated on a surface of an area sensor 501.
[0197] Next, a configuration of the optical system (OCT portion) is
described.
[0198] In this embodiment, the OCT imaging portion 102 has a
configuration in which a part of the optical system is constituted
of optical fibers for downsizing the apparatus.
[0199] The configuration of this embodiment is the same as the
configuration of the first embodiment except for that the measuring
optical system is constituted of the fundus camera main body
portion 300.
[0200] Components identical to or corresponding to the components
illustrated in FIG. 1 of the first embodiment are denoted by the
same reference numerals, and hence repetitive description thereof
is omitted.
[0201] First, an overall schematic configuration of an optical
system of the OCT apparatus 102 according to this embodiment is
described.
[0202] FIG. 11 is a diagram illustrating the overall schematic
configuration of the optical system of the OCT apparatus 102
according to this embodiment.
[0203] In FIG. 11, the OCT imaging portion is represented by 102; a
light source, 101; emitted beams, 104, 104-1, 104-2, and 104-3;
reference beams, 105-1, 105-2, and 105-3; measuring beams, 106-1,
106-2, and 106-3; multiplexed beams, 142-1, 142-2, and 142-3;
single mode fibers, 110 and 148; lenses, 135-1, 135-2, 135-3, and
135-4; and a mirror, 114.
[0204] Dispersion compensation glass is represented by 115; an
electrical stage, 117-1; and a personal computer, 125. Optical
couplers are represented by 131-1, 131-2, 131-3, and 156; a line
camera, 139; a frame grabber, 140; transmission gratings, 141;
polarization controllers, 153-1, 153-2, 153-3, and 153-4; and fiber
length adjusting devices, 155-1, 155-2, and 155-3.
[0205] As illustrated in FIG. 11, the OCT apparatus 100 of this
embodiment constitutes a Michelson interference system as a
whole.
[0206] In FIG. 11, the emitted beam 104 that is a beam emitted from
the light source 101 is split by the optical coupler 156 into the
three emitted beams 104-1, 104-2, and 104-3.
[0207] Further, the emitted beams 104-1, 104-2, and 104-3 pass
through the polarization controller 153-1, and are split, by the
optical couplers 131-1, 131-2, and 131-3, into the reference beams
105-1, 105-2, and 105-3 and the measuring beams 106-1, 106-2, and
106-3, respectively, with an intensity ratio of 50:50.
[0208] The measuring beams 106-1, 106-2, and 106-3 are returned as
return beams 108-1, 108-2, and 108-3 that have been, via the
connector 154, the adapter 400, and the fundus camera main body
portion 300, reflected or scattered by the retina 127 of the object
eye 107 to be monitored (FIG. 10). Then, the return beams 108-1,
108-2, and 108-3 are multiplexed with the reference beams 105-1,
105-2, and 105-3 by the optical couplers 131-1, 131-2, and
131-3.
[0209] After the reference beams 105-1, 105-2, and 105-3 and the
return beams 108-1, 108-2, and 108-3 are multiplexed with each
other, the resultant beams are dispersed according to the
wavelengths by the transmission gratings 141, and input to the line
camera 139. The line camera 139 converts a light intensity into a
voltage for each position (wavelength), and the tomographic image
of the object eye 107 is generated by using the voltage
signals.
[0210] Next, the light source 101 and matters relevant thereto are
described.
[0211] The light source 101 is a super luminescent diode (SLD),
which is a typical low coherence light source. The light source 101
has a wavelength of 830 nm and a bandwidth of 50 nm.
[0212] Here, the bandwidth is an important parameter because the
bandwidth affects the resolution of the obtained tomographic image
in the optical axis direction.
[0213] In addition, the light source of an SLD type is used in this
embodiment, but an amplified spontaneous emission (ASE) type or the
like may also be used as long as the light source emits a low
coherence beam.
[0214] In addition, concerning the wavelength of light,
near-infrared light is suitable because the light is used for
measuring an eye. Further, because the wavelength affects the
resolution of the obtained tomographic image in the lateral
direction, the wavelength is desirably as short as possible. Here,
the wavelength is 830 nm. Depending on the measurement site to be
monitored, another wavelength may be selected.
[0215] Next, optical paths of the reference beams 105-1, 105-2, and
105-3 are described.
[0216] The reference beams 105-1, 105-2, and 105-3 split by the
optical couplers 131-1, 131-2, and 131-3 pass through the
polarization controller 153-2 and the fiber length adjusting
devices 155-1, 155-2, and 155-3. Then, the resultant beams are
converted into parallel beams having a beam diameter of 1 mm by the
lenses 135-1, and are then emitted.
[0217] Next, the reference beams 105-1, 105-2, and 105-3 pass
through the dispersion compensation glass 115, and are condensed
onto the mirror 114 by the lenses 135-2.
[0218] Next, the reference beams 105-1, 105-2, and 105-3 change the
direction at the mirror 114, and are guided toward the optical
couplers 131-1, 131-2, and 131-3 again.
[0219] Next, the reference beams 105-1, 105-2, and 105-3 pass
through the optical couplers 131-1, 131-2, and 131-3, and are
guided to the line camera 139.
[0220] The dispersion compensation glass 115 compensates for
dispersion that occurs when the measuring beams 106-1, 106-2, and
106-3 travel to and from the object eye 107, with respect to the
reference beams 105-1, 105-2, and 105-3, respectively.
[0221] Here, assuming a value typical as an average diameter of the
eyeball of Japanese people, L is set to 23 mm.
[0222] Further, the electrical stage 117-1 is capable of moving in
directions indicated by arrows, which enables adjusting and
controlling the optical path lengths of the reference beams 105-1,
105-2, and 105-3.
[0223] In addition, the electrical stage 117-1 can be controlled by
the personal computer 125 at high speed.
[0224] Further, the fiber length adjusting devices 155-1, 155-2,
and 155-3 are installed for the purpose of making fine adjustment
on the respective fiber lengths, and are capable of adjusting the
optical path lengths of the reference beams 105-1, 105-2, and 105-3
according to the respective measurement sites of the measuring
beams 106-1, 106-2, and 106-3. The personal computer 125 can
control the fiber length adjusting devices 155-1, 155-2, and
155-3.
[0225] Next, the optical paths of the measuring beams 106-1, 106-2,
and 106-3 are described.
[0226] The measuring beams 106-1, 106-2, and 106-3 split by the
optical couplers 131-1, 131-2, and 131-3 pass through the
polarization controller 153-4. Then, via the connectors 154, the
single mode fibers 148, the adapter 400, and the fundus camera main
body portion 300, the measuring beams 106-1, 106-2, and 106-3 are
guided to the retina 127 of the object eye 107 (see FIG. 10).
[0227] After entering the object eye 107, the measuring beams
106-1, 106-2, and 106-3 are reflected or scattered by the retina
127 to become the return beams 108-1, 108-2, and 108-3.
[0228] The return beams 108-1, 108-2, and 108-3 are guided to the
optical couplers 131-1, 131-2, and 131-3 again via the fundus
camera main body portion 300, the adapter 400, the connectors 410,
the single mode fibers 148, and the connectors 154 in the stated
order.
[0229] The above-mentioned reference beams 105-1, 105-2, and 105-3
and the above-mentioned return beams 108-1, 108-2, and 108-3 are
multiplexed with each other by the optical couplers 131-1, 131-2,
and 131-3, respectively, and then split in half.
[0230] Then, the multiplexed beams 142-1, 142-2, and 142-3 are
dispersed according to the wavelengths by the transmission gratings
141, and condensed by the lenses 135-3. Then, the intensity of
light is converted into voltage for each position (wavelength) by
the line camera 139.
[0231] Specifically, an interference pattern of the spectral region
along the wavelength axis is monitored on the line camera 139.
[0232] Next, a configuration of a measurement system of the OCT
apparatus according to this embodiment is described.
[0233] The OCT imaging portion 102 is capable of obtaining a
tomographic image (OCT image) generated based on the intensities of
interference signals from a Michelson interference system.
[0234] To give further description of the measurement system, the
return beams 108-1, 108-2, and 108-3 reflected or scattered by the
retina 127 are multiplexed with the reference beams 105-1, 105-2,
and 105-3 by the optical couplers 131-1, 131-2, and 131-3,
respectively. Then, the multiplexed beams 142-1, 142-2, and 142-3
are dispersed according to the wavelengths by the transmission
gratings 141, and condensed by the lenses 135-3. The intensity of
light is converted into voltage for each position (wavelength) by
the line camera 139.
[0235] Specifically, in association with the number of the
measuring beams 106-1, 106-2, and 106-3, the line camera 139
monitors interference patterns of spectral regions along three
wavelength axes.
[0236] A voltage signal group thus obtained is converted into
digital values by the frame grabber 140. After that, the personal
computer 125 performs data processing to form a tomographic
image.
[0237] Here, the line camera 139 has 4,096 pixels, and uses 3,072
pixels thereof to obtain the intensity of each of the respective
wavelengths (divided into 1,024 positions) of the multiplexed beams
142-1, 142-2, and 142-3.
[0238] Next, a method of obtaining a tomographic image is
described.
[0239] The method of obtaining a tomographic image by using the OCT
apparatus is substantially the same as in the first embodiment, and
hence description thereof is omitted.
[0240] The OCT apparatus 200 controls the XY scanner 408, and, by
obtaining the interference pattern by the line camera 139, the
tomographic image of the retina 127 may be obtained (FIG. 10).
[0241] Next, a configuration of a measuring beam monitoring system
is described.
[0242] The configuration of the measuring beam monitoring system,
which is a characteristic of the present invention, is
substantially the same as in the first embodiment except for that
the monitoring camera 321 is installed inside the fundus camera
main body portion 300, and hence repetitive description thereof is
omitted.
[0243] The OCT apparatus 200 uses the monitoring camera 321
installed inside the fundus camera main body portion 300 to monitor
the measuring beams 106-1, 106-2, and 106-3 in the vicinity of the
cornea 126, which enables adjusting the relative positions of the
OCT apparatus 200 and the object eye 107.
[0244] Further, the adjustment may be performed by using the
fixation lamp 320, the face fixation unit 323, the personal
computer 125, and the like.
Other Embodiments
[0245] Aspects of the present invention may also be realized by a
computer of a system or apparatus (or devices such as a CPU or MPU)
that reads out and executes a program recorded on a memory device
to perform the functions of the above-described embodiment(s), and
by a method, the steps of which are performed by a computer of a
system or apparatus by, for example, reading out and executing a
program recorded on a memory device to perform the functions of the
above-described embodiment(s). For this purpose, the program is
provided to the computer for example via a network or from a
recording medium of various types serving as the memory device
(e.g., computer-readable medium).
[0246] While the present invention has been described with
reference to exemplary embodiments, it is to be understood that the
invention is not limited to the disclosed exemplary embodiments.
The scope of the following claims is to be accorded the broadest
interpretation so as to encompass all such modifications and
equivalent structures and functions.
[0247] This application claims the benefit of Japanese Patent
Application No. 2008-331925, filed Dec. 26, 2008, which is hereby
incorporated by reference herein in its entirety.
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